Date

Author

Metadata

Share

Abstract

Asian catfish Clarias macrocephalus is an esteemed food fish especially in Southeast Asia due to its tender and delicious meat. This commodity constitutes a valuable fishery for small-scale fishers in the region and has a great potential for aquaculture. The important considerations in the grow-out culture of catfish are reliable water supply, soil with good compaction properties for dike construction, supply of fingerlings, feeds, labor, pond supplies and technology assistance. The farm must also be accessible by road, near to market facilities and has a peaceful environment. Rearing catfish in ponds is the most popular and commonly practiced. The pen culture is a system fully enclosed by nets on all sides but utilizes the dug-out pond, dam or lake bed as bottom enclosure. Tanks in abandoned old hatcheries with freshwater source can be used for catfish culture. In the cage culture system the stock is fully enclosed by nylon nets on all sides and bottom similar to an inverted mosquito net installed in suitable areas like reservoirs, dams, lakes and dug-out ponds. The rice-fish (catfish) culture is also practiced where the rice pond canals are utilized to retain water at 1-2 m depth to provide shelter to the fish while the rice plot maintains 10-20 cm water depth. For the stock, select fingerlings that are active, healthy and uniform in size. Handling of fish stock is important to avoid mortality due to stress during harvest, sorting, counting and transport. Furthermore, stocking of fish is recommended during the cooler part of the day. Catfish fingerlings stocking density is about 5 to 20 pcs/m2 depending on the water supply and support facilities of the farm. The catfish, C. macrocephalus, requires a substantial amount of dietary protein for growth. For this species a formulated diet with crude protein (CP) of 34%, moist diet (trash fish or blanched chicken entrails plus rice bran or cooked broken rice), and a combination of pellet feeds (50%) and moist diet (50%) have been tested and acceptable for the grow-out culture. Economic evaluation based on a grow-out culture in pond with an area of 1,000 m2 showed that feeds and fingerlings are the major variable costs. The net income, return on investments and payback period, respectively range from PhP22,972-PhP35,741, 80-122% and 0.8-1.2 years when using pellet, moist feed or a combination of these feeds. Feeding using formulated diet has an advantage of convenience, quality and quantity over moist diet which has issues such as inconsistent supply, storage requirement and fouling the rearing water.

Aquaculture practised in Thailand is in the form of pond culture and cage culture in freshwater, brackishwater and coastal areas. The main species cultured include freshwater prawns, brackishwater shrimp, cockles, mussels, and various freshwater and marine finfishes. There is good potential for increased production from freshwater, brackishwater and marine aquaculture. However, the 1983 production of 145 000 mt represents only about 6% of Thailand's total fish production and production in this subsector has fluctuated widely. It will be several years before aquaculture production will contribute substantially to total production. Nonetheless, the culture of high value species of shrimp and fish could contribute significantly to export earnings during the next 5 to 10 years.

Conducted primarily by government agencies, research and development are along the lines of increasing seed supply, establishing new culture techniques or improving older ones. The Department of Fisheries (DOF) together with some private companies have ventured into the development and testing of artificial diets for the various cultured species using a variety of indigenous feed stuffs.

It is estimated that with adequate investments and appropriate support, aquaculture production will increase from 145 000 mt in 1983 to 378 000 mt in 1991, showing an annual increase of about 13% over this period. Major increases would come from bivalve mariculture (131 000 mt), brackishwater ponds (36 000 mt) freshwater ponds (46 000 mt) and brackishwater cage culture (20 000 mt).

A non-fish meal diet using plant and/or animal protein materials for yellowtail, Seriola quinqueradiata was developed. Three kinds of non-fish meal diets and a control diet containing 50% fish meal were processed. In the non-fish meal diets, the fish meal was replaced with commercially available plant or animal materials and supplemented with taurine and other ingredients for maintaining palatability. These diets were fed to one year old yellowtail (body weight: 753±96 g) in net cages. No significant differences in growth, daily weight gain, daily feed rate, feed conversion ratio and protein efficiency ratio were observed among fish given the diets. Non-fish meal diets were processed in a factory and their biological characteristics were studied such as uptake, stomach evacuation rate, and disease resistance. In addition, the diet palatability of each substitute protein source for fish was examined and ingredients that enhanced palatability of the non-fish meal diets were identified. Non-fish meal diets have the potential to support the growth of one year old yellowtail.

Cultured marine aquatic species are predominantly carnivorous. Major species in the region are seabass, grouper, snapper, tiger shrimp, mangrove crab and abalone. These species, except for abalone, require a high level of dietary protein mostly supplied by marine sources such as fish meal. Global production of marine fish and marine shrimps showed a 3-4 fold increase from 1995 to 2010. For the same period, the usage of commercial feed for production of marine fish and shrimps increased while the fish meal portion in the formulation decreased. This is indicative of fish meal being substituted with alternative sources in commercial feed production, and to some extent the substitution of marine oil which particularly improved the FCR for the marine fish production from 2.0 to 1.9 and for marine shrimps from 2.0 to 1.6.

Plant products that include cereal grains, legumes and oilseeds have the most potential among the alternative ingredients for use in aquafeed. The use of these resources for high value marine species is limited due to a variety of anti-nutritional substances they contain. Removal of these substances by processing techniques has improved utilization but with added cost. Hence, fish meal is still the primary source of protein for marine carnivores and its substitution with higher amounts of alternative plant proteins may be difficult compared with lower levels of replacements. The Asian region has accounted for the more than 50% of the total global aquaculture production in 2012 with indications of increased utilization of alternative protein sources in commercial feed production. For the major marine species in the region the increasing trend of plant protein usage with the targeted levels of substitution of fish meal with plant protein sources should be sustainable.